Coenzyme AdoB12 vs AdoB12.-homolytic Co-C cleavage following electron transfer: a rate enhancement greater than or equal to 10(12).
Comparison of the 25 degrees C Co-C bond homolysis rate constant of adenosyl-cobalamin (coenzyme B12) vs that for electrochemically reduced adenosyl-cobalamin radical anion indicates a rate enhancement of at least 10(12 +/- 2) upon the addition of one antibonding electron. Even though electrochemical reduction promotes Co-C homolysis by virtually the same amount as the 10(12 +/- 1) enzymic activation seen for adenosylcobalamin, electron-transfer activation of the Co-C homolysis in adenosylcobalamin-dependent enzyme reactions is considered unlikely, based on four lines of evidence.
Finke
R G
RG
Department of Chemistry, University of Oregon, Eugene 97403-1253.
Martin
B D
BD
D003038:Cobamides / Q000737:chemistry / Q000378:metabolism*; D004579:Electron Transport; D007700:Kinetics; D014805:Vitamin B 12 / Q000737:chemistry / Q000378:metabolism*
D003038:Cobamides; C000913:cobamamide; D014805:Vitamin B 12